Fuse



Patented Oct. 29,1946

FUSE

William 0. Schultz, South Milwaukee, Wis., as-

signor to Line Material Company, Milwaukee, Wis., a corporation of Delaware Application June 25, 1943, Serial No. 492,291

This invention relates to power fuses and more particularly to fuses of the bayonet type.

In certain cases where bayonet type fuses are employed it is desirable to use standard fuselinks of the type which does not include a builtin biasing spring; but at the same time it often isdesirable or necessary to provide suitable spring means operative to bias the link and thereby quicken the separation of severed fuse-link parts when blowouts occur.

The primary object of the present invention is to devise a practical fuse construction which is Well adapted to utilization of standard links of the above-indicated variety while providing the desired spring bias.

Another object is to achieve simplicity of design and consequent manufacturing economy.

Still another object is to facilitate the installation of replacement fuse-links so that servicing of the fuses in the field will not be inordinately time-consuming or entail the exercise of any considerable skill.

A further object is to provide a movable springbiased fuse-link engagin member urged to fuselink extracting position and normally engaged by a resilient friction contact which relieves the fuse-link of excessive stresses while the fuse-cartridge containing the fuse-link is in circuit closing position, and also to so correlate the biasing spring with the fuse structure as to protect it from the destructive effects of an are upon rupture of the fuse link.

' A prominent feature of the present invention resides in a novel fuse-cartridge terminal construction which incorporates within itself both a biasing spring and contact members, so coordinated as to facilitate insertion and withdrawal of the cartridge into and from the fuse housing without requiring any electrical connection to be made by the serviceman after the cartridge is in place, and so designed that the fuse-link is properly and fully spring-biased before the cartridge is inserted in the housing, and so continues thereafter.

Another feature consists in the provision of a simple metal terminal clip which can easily be applied to the flexible leader of a standard fuselink and which is of such dimensions that it can be passed through the fuse cartridge bore while attached to the fuse-link leader and thereafter bent, without difiiculty, so as to effect an anchoring engagement and good electrical contact between the fuse-link and the adjacent cartridge terminal while contemporaneously retaining the biasing spring under compression and. thus in 5 Claims. (Cl. 200-117) readiness to function as an expeller in event of a blowout.

A preferred embodiment of the invention is illustrated by the accompanying drawing, whereof:

Fig. l is a sectional view depicting the lower end portion of a bayonet fuse housing together with a fuse-cartridge and fuse-link-the cartridge and link being shown during an intermediate stage of link installation;

Fig. 2 is substantially a repetition of the lower portion of Fig. 1, except that it depicts the fuselink fully installed and shows the ears of the metal clip bent to effect an anchorage of the fuse-link to the cartridge terminal and biasing pri Fig. 3 is a view taken along the line 3--3 of Fig. 2; and- Fig. 4 is a view taken along the line 44 of Fig. 2

Inasmuch as the present invention is not concerned with the fuse housing construction, there has been shown only the lower portion of such a housing. This comprises a tubular porcelain housing member I, shown fragmentarily, in which is located a conductive sleeve 2 secured within the housing by means of a cement or fusible metal filler 3. Sleeve 2 is suitably apertured at 2a to receive a line conductor and is provided with one or morebinding screws 4 by means of which the line conductor is clamped. The sleeve is bored at 2?) concentrically with the housing to receive and make electrical contact with the lower terminal of the fuse-cartridge, which latter is insertable into and withdrawable from said sleeve via the upper end of the housing.

The fuse-cartridge comprises an elongate tube 5 of horn fiber or, preferably, of Bakelite lined with horn fiber, and is threaded externally at its upper end to receive a ferrule '6 which, in turn is threaded to receive a removable conductive cap I. The upper ferrule and cap designs are to be regarded as purely conventional and subject to a. variety of modifications. The invention does not lie in that part of the structure.

There is secured to tube 5, toward the lower end, a metal thimble 8. This encircles the tube and provides support for the upper end of a tubular member 9 which is slotted lengthwise to form several depending resilient contact fingers 9a spaced circumferentially about tube 5. These contact fingers are yieldable radially of the tube and are designed to eifect spring-pressed engagement with the bore 2b of sleeve 2.

The lower end of thimble 8 is of reduced diameter and threaded to engage the upper end of a helical spring H) for which it affords an anchorage. Said spring encircles the lower end of tube 5 and is secured at its lower end to a terminal member II, which is supported by the spring and is movable axially of tube 5 by stretching and compressing the spring.

The spring I is disposed, in its entirety, exteriorly of the tube and the terminal member ll. Consequently, any are established during circuit operations will not cause injury to the spring since the latter is positioned out of the path of hot destructive gases generated by the are and expelled from the tube.

The fuse link 12 is of a standard type comprising a fusible section l3 together with a button-head upper terminal l4 and a flexible con-- ductive leader [5. Button head terminal I4 is gripped between ferrule 6 and cap I and serves as means for supporting the link at'its upper end as well as for effecting electrical connection thereto.

A tubular metal clip 16 is compressed upon and thereby secured to leader H3 at a predetermined point. As shown in Fig. 1, clip 15 has two o-p-- posite downwardly extending pliable fingers Ilia and Nib, which fingers are designed to be bent outwardly and upwardly, as shown in Fig. 2, to hookingly engage terminal member I l-see Figs. 2 and 3.

Since the fuse-link must be inserted in the cartridge from the upper end thereof, it is obvious that metal clip l5 must initially be di-- mensioned to pass through the bore of tube 5. Hence, fingers lSa and [6b are made to extend parallel to leader l5, as shown in Fig. l, but capable easily of being bent to form laterally extending ears, as shown in Fig. 2, after the fuse-link is in place.

When the fuse-link is fully installed, spring I0 is under compression and the link correspondingly under tension; but when free, the spring is extended lengthwise so that terminal member ll occupies a lower position, as indicated in dot and dash lines in Fig. 1. Said spring must be compressed by forcing terminal member (I to approximately the position in which it is shown in full lines in Fig. 1, before the fingers lSa and 46b are bent outwardly and upwardly, per Fig. 2, to form the aforementioned ears which hookingly engage said terminal member. Whenever necessary, fingers 16a and [6b can be bent back to approximately their original form, thus permitting the fuse-link to be removed from the cartridge.

Terminal member I I is contacted by the lower ends of contact fingers 9a, thereby establishing a conductive path via said contact fingers between sleeve 2 and terminal member I l Accordingly, spring II] is not required to carry enough current to cause injury thereto.

Terminal member II is, preferably, a brass casting formed to present at its lower end two spaced parallel fiat sides which, in Fig. 3, are identified by reference numerals Ila and llb. Said fiat sides are effective to provide ample contact area with ears Ilia and lfib, while at the same time serving to prevent rotation of clip !6 relatively to said terminal member after the link is installed.

The resilient contact fingers 9a frlctio-nally engage the terminal member H and are bowed radially outwardly of the tube 5, as clearly illustrated in the drawing, to frictionally engage the conductive sleeve 2. It is contemplated that the frictional engagement of the contact fingers 9a with the terminal member H and conductive sleeve 2 will be of sufficient magnitude to effectively counteract the expansive force of the spring I!) and thus relieve the fuse-link l2 of the greater part of the stresses which would otherwise be imposed thereon by the expansive forces of the spring. It will of course be understood that frictional forces exerted by the contact fingers 9a will not entirely overcome the expansive forces of the spring l0 since the spring must be free to withdraw the flexible leader 15 upon rupture of the fusible section 13 of the fuse-link.

When the fuse-link blows, spring I0 is effective quickly to withdraw and expel from the cartridge all that portion of the fuse-link which is below the point where disjunction occurs.

What is claimed is:

1. In combination, a fuse-cartridge, a fuselink within said cartridge and having a terminal anchored at one end of said cartridge, the other end of said cartridge being open, said fuse-link including as its second terminal an elongate conductive leader projecting out of said open end of the cartridge, a helical spring encircling said cartridge adjacent said open end, one end only of said spring being anchored to said cartridge at a point somewhat removed from the open end thereof, a tubular member encircling said spring and attached at one end to said cartridge, said tubular member comprising a plurality of resilient contact fingers extending lengthwise of said cartridge, and means carried by said leader for anchoring said leader to the unanchored end of said spring for maintaining said spring under compression and said fuse-link under tension, said means being engaged by said resilient contact fingers whereby the expansive force of said spring is in part nullified.

2. In a fuse of the class described, a fuse cartridge having an open end, an expansible spring encircling said open end and having one end thereof secured to said cartridge at a point remote from said open end, a tubular terminal secured to the other end of said spring having a bore concentric with and receiving the open end of said tube, said tubular terminal in part being encircled by said spring, a contact member secured to said cartridge and encircling said spring and said terminal, said contact member including contact fingers frictionally engaging said terminal, and a fuse link engaging said terminal and normally holding said spring under compression.

3. In combination, a fuse cartridge, a fuse link of the standard type within said cartridge having a terminal anchored at the upper end of said cartridge, the other end of said cartridge being open, said fuse link having as its other terminal a flexible conductive leader projecting out of the open end of the cartridge, a spring encircling said cartridge at its lower end and having one end anchored thereto, a terminal member carried by the other end of said spring at a point adjacent the open end of said cartridge, said terminal member having a passageway co-terminous with said open end of the cartridge and generally coaxial therewith, a metal clip attached to said flexible leader and having a plurality of pliable fingers which initially extend generally parallel to said leader so as to enable said clip to pass through the bores of said cartridge and terminal member, said fingers being bent after passing through the bores of said cartridge and terminal member to form ears projecting radially from said leader and engaging said terminal member whereby said spring is maintained under compression and said fuse link is tensioned, and a, resilient contact carried by said cartridge frictionally engaging said terminal member to provide a counteracting force which in part nullifies the expansive force of said spring.

4. In combination, a fuse cartridge, a fuse link having a flexible leader within said cartridge and having a terminal anchored on one end of said cartridge, the other end of said cartridge being open, a biasing spring encircling said cartridge near the open end thereof, and having one end anchored to said cartridge, a movable terminal member carried by the other end of said spring, said fuse link including as its second terminal a pair of bendable arms, said arms, when bent, being operative to engage said movable terminal member and to hold said spring under compression and said fuse link under tension, and a resilient contact carried by said cartridge frictionally engaging said movable terminal member and in part nullifying the forces imposed on said fuse link by said spring.

5. In combination, a fuse cartridge, a fuse link having a flexible leader Within said cartridge and having a terminal anchored at the upper end of said cartridge, the other end of said cartridge being open, a spring encircling said cartridge at its lower end and having one end anchored thereto, a tubular terminal member carried by the other end of said spring and having a bore concentric with and receiving the open end of said tube, said flexible leader having at its lower end a plurality of bendable arms, said arms being bent after passing through the bores of said cartridge and terminal member to form ears projecting radially from said leader and being effective to hold said spring under compression and to tension said fuse link, and a resilient contact carried by said cartridge frictionally engaging said terminal members to provide a counteracting force which in part nullifies the expansive force of said spring.

WILLIAM O. SCHULTZ. 

